diff --git a/crates/ely_app/src/shell/gpui_harness_tests.rs b/crates/ely_app/src/shell/gpui_harness_tests.rs
index 579f918..d4da887 100644
--- a/crates/ely_app/src/shell/gpui_harness_tests.rs
+++ b/crates/ely_app/src/shell/gpui_harness_tests.rs
@@ -444,598 +444,6 @@ async fn baseline_overlay_under_overflow_hidden_relative_receives_click(cx: &mut
     );
 }
 
-/// Bisect probe layer 2: stack the full ElyShell wrapper chain that
-/// sits between the window root and the overlay — root size_full,
-/// absolute inset_0 flex container, flex_1 + flex_col main pane with
-/// rounded/border/shadow/overflow_hidden, flex_1 content wrapper,
-/// then the relative+overflow_hidden surface wrapper from
-/// `render_web_surface`. If this passes, the bug is in something
-/// `render_external_web_canvas` adds (not in the plain layout chain).
-#[gpui::test]
-async fn baseline_overlay_under_full_elyshell_wrapper_chain_receives_click(
-    cx: &mut TestAppContext,
-) {
-    let click_count = Rc::new(RefCell::new(0u32));
-    let counter_for_render = click_count.clone();
-
-    struct DeepProbe {
-        on_up_counter: Rc<RefCell<u32>>,
-    }
-    impl Render for DeepProbe {
-        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
-            let counter = self.on_up_counter.clone();
-            // Root: matches render_browser's outer div.
-            div().size_full().child(
-                // Absolute flex container matches render_browser's child layout.
-                div().absolute().inset_0().p(px(16.0)).gap(px(12.0)).flex().child(
-                    // Main pane: matches render_main_pane.
-                    div()
-                        .flex_1()
-                        .h_full()
-                        .min_w_0()
-                        .flex()
-                        .flex_col()
-                        .rounded(px(18.0))
-                        .border_1()
-                        .overflow_hidden()
-                        .child(
-                            // Content wrapper: matches the flex_1 child of main_pane.
-                            div().flex_1().overflow_hidden().child(
-                                // Surface wrapper: matches render_web_surface root.
-                                div().relative().size_full().min_w_0().overflow_hidden().child(
-                                    div()
-                                        .absolute()
-                                        .size_full()
-                                        .occlude()
-                                        .on_mouse_down(MouseButton::Left, |_event, _window, _cx| {})
-                                        .capture_any_mouse_up(move |_event, _window, _cx| {
-                                            *counter.borrow_mut() += 1;
-                                        })
-                                        .on_mouse_move(|_event, _window, _cx| {})
-                                        .on_scroll_wheel(|_event, _window, _cx| {}),
-                                ),
-                            ),
-                        ),
-                ),
-            )
-        }
-    }
-
-    let (_probe, cx) =
-        cx.add_window_view(|_window, _cx| DeepProbe { on_up_counter: counter_for_render });
-    cx.run_until_parked();
-
-    cx.simulate_mouse_move(point(px(400.0), px(400.0)), None, Modifiers::default());
-    cx.simulate_click(point(px(400.0), px(400.0)), Modifiers::default());
-    cx.run_until_parked();
-
-    assert_eq!(
-        *click_count.borrow(),
-        1,
-        "Bisect layer 2: the full root → absolute-flex → main-pane → \
-         content-wrapper → surface-wrapper chain (sans listeners) \
-         should still deliver the click. If this fails, the bug is in \
-         this wrapper chain itself; if it passes, the bug is in \
-         something render_external_web_canvas adds (canvas tracker, \
-         absolute content wrapper sibling, or a gpui-component widget)."
-    );
-}
-
-/// Diagnostic probes (T13 bisect): each layer of the ElyShell render
-/// tree was reproduced in isolation and **all passed**, confirming the
-/// listener combo, layout wrapper chain, canvas sibling, entity
-/// update side effects, and track_focus root listeners are NOT the
-/// cause. The bug is elsewhere — likely in ElyShell::new's setup
-/// (subscriptions, timer, InputState side effects) or in the
-/// sync_address_input call inside navigate_active_tab that mutates
-/// Input widget state which may invalidate the rendered_frame
-/// between MouseMove and MouseUp. Kept for regression coverage.
-/// T13 layer 6: replicate ElyShell::new's gpui-component widget
-/// construction (InputState creation + subscription) on top of the
-/// passing layout, then click. If this fails, the InputState entity
-/// or its subscription is what breaks hit_test for descendant
-/// occlude divs.
-#[gpui::test]
-async fn baseline_overlay_with_input_state_construction_receives_click(cx: &mut TestAppContext) {
-    use gpui::AppContext;
-    use gpui::Entity;
-    use gpui::Subscription;
-    use gpui_component::input::{InputEvent, InputState};
-
-    cx.update(gpui_component::init);
-
-    let click_count = Rc::new(RefCell::new(0u32));
-    let counter_for_render = click_count.clone();
-
-    struct ProbeWithInput {
-        on_up_counter: Rc<RefCell<u32>>,
-        _command_input: Entity<InputState>,
-        _command_subscription: Subscription,
-    }
-    impl Render for ProbeWithInput {
-        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
-            let counter = self.on_up_counter.clone();
-            div().relative().size_full().min_w_0().overflow_hidden().child(
-                div()
-                    .absolute()
-                    .size_full()
-                    .occlude()
-                    .on_mouse_down(MouseButton::Left, |_e, _w, _c| {})
-                    .capture_any_mouse_up(move |_e, _w, _c| {
-                        *counter.borrow_mut() += 1;
-                    })
-                    .on_mouse_move(|_e, _w, _c| {})
-                    .on_scroll_wheel(|_e, _w, _c| {}),
-            )
-        }
-    }
-
-    let (_probe, cx) = cx.add_window_view(|window, cx| {
-        let command_input = cx.new(|cx| InputState::new(window, cx).placeholder("test"));
-        let command_subscription = cx.subscribe_in(
-            &command_input,
-            window,
-            |_probe: &mut ProbeWithInput, _input, _event: &InputEvent, _window, _cx| {
-                // mimic the shape ElyShell::new uses
-            },
-        );
-        ProbeWithInput {
-            on_up_counter: counter_for_render,
-            _command_input: command_input,
-            _command_subscription: command_subscription,
-        }
-    });
-    cx.run_until_parked();
-
-    cx.simulate_mouse_move(point(px(400.0), px(400.0)), None, Modifiers::default());
-    cx.simulate_click(point(px(400.0), px(400.0)), Modifiers::default());
-    cx.run_until_parked();
-
-    assert_eq!(
-        *click_count.borrow(),
-        1,
-        "Bisect layer 6: an InputState entity + a subscribe_in to it \
-         must not break click delivery to a sibling occlude div. If \
-         this fails, the InputState construction (which spawns \
-         BlinkCursor, registers window-activation/focus/blur \
-         observers) corrupts hit_test for the rest of the tree."
-    );
-}
-
-/// T13 next-layer diagnostic: same shape as the passing baseline
-/// (`.relative().size_full().min_w_0().overflow_hidden()` parent +
-/// the input_overlay listener combo) but with `gpui_component::init`
-/// called first. The real ElyShell test calls init; the probes
-/// don't. If this fails, `gpui_component::init`'s side effect on
-/// the App is what breaks the rendered_frame's hitbox registration
-/// for descendant occlude divs.
-#[gpui::test]
-async fn baseline_overlay_after_gpui_component_init_receives_click(cx: &mut TestAppContext) {
-    cx.update(gpui_component::init);
-
-    let click_count = Rc::new(RefCell::new(0u32));
-    let counter_for_render = click_count.clone();
-
-    struct AfterInitProbe {
-        on_up_counter: Rc<RefCell<u32>>,
-    }
-    impl Render for AfterInitProbe {
-        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
-            let counter = self.on_up_counter.clone();
-            div().relative().size_full().min_w_0().overflow_hidden().child(
-                div()
-                    .absolute()
-                    .size_full()
-                    .occlude()
-                    .on_mouse_down(MouseButton::Left, |_e, _w, _c| {})
-                    .capture_any_mouse_up(move |_e, _w, _c| {
-                        *counter.borrow_mut() += 1;
-                    })
-                    .on_mouse_move(|_e, _w, _c| {})
-                    .on_scroll_wheel(|_e, _w, _c| {}),
-            )
-        }
-    }
-
-    let (_probe, cx) =
-        cx.add_window_view(|_window, _cx| AfterInitProbe { on_up_counter: counter_for_render });
-    cx.run_until_parked();
-
-    cx.simulate_mouse_move(point(px(400.0), px(400.0)), None, Modifiers::default());
-    cx.simulate_click(point(px(400.0), px(400.0)), Modifiers::default());
-    cx.run_until_parked();
-
-    assert_eq!(
-        *click_count.borrow(),
-        1,
-        "Bisect: gpui_component::init must not break click delivery to \
-         an occlude div with the input_overlay listener combo. If this \
-         fails, init registers some App-level state that interferes \
-         with rendered_frame hitbox registration for descendants."
-    );
-}
-
-/// Bisect probe layer 5: the full chain WITH the root-level
-/// `track_focus + on_mouse_up(Left, bubble)` listeners ElyShell
-/// puts on its outermost div. If track_focus's auto-focus MouseDown
-/// handler, or the root's bubble-phase MouseUp listener, somehow
-/// invalidates the rendered_frame between MouseDown and MouseUp,
-/// input_overlay's hitbox will no longer match the listener
-/// snapshot's id and `is_hovered` will return false. That's the
-/// exact symptom we see: hover_point is None too, so it's not
-/// capture-specific — every listener on input_overlay is missing
-/// its hit.
-#[gpui::test]
-async fn baseline_overlay_under_root_with_track_focus_receives_click(cx: &mut TestAppContext) {
-    use gpui::FocusHandle;
-
-    let click_count = Rc::new(RefCell::new(0u32));
-    let move_count = Rc::new(RefCell::new(0u32));
-    let counter_for_up = click_count.clone();
-    let counter_for_move = move_count.clone();
-
-    struct TrackFocusProbe {
-        focus: FocusHandle,
-        on_up_counter: Rc<RefCell<u32>>,
-        on_move_counter: Rc<RefCell<u32>>,
-    }
-    impl Render for TrackFocusProbe {
-        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
-            let counter_up = self.on_up_counter.clone();
-            let counter_move = self.on_move_counter.clone();
-            div()
-                .size_full()
-                .track_focus(&self.focus)
-                .on_mouse_up(MouseButton::Left, |_event, _window, _cx| {})
-                .child(
-                    div().absolute().inset_0().p(px(16.0)).gap(px(12.0)).flex().child(
-                        div()
-                            .flex_1()
-                            .h_full()
-                            .min_w_0()
-                            .flex()
-                            .flex_col()
-                            .rounded(px(18.0))
-                            .border_1()
-                            .overflow_hidden()
-                            .child(
-                                div().flex_1().overflow_hidden().child(
-                                    div()
-                                        .relative()
-                                        .size_full()
-                                        .min_w_0()
-                                        .overflow_hidden()
-                                        .child(div().absolute().inset_0().child(div().size_full()))
-                                        .child(
-                                            canvas(move |_b, _w, _c| {}, |_, _, _, _| {})
-                                                .absolute()
-                                                .size_full(),
-                                        )
-                                        .child(
-                                            div()
-                                                .absolute()
-                                                .size_full()
-                                                .occlude()
-                                                .on_mouse_down(MouseButton::Left, |_e, _w, _c| {})
-                                                .capture_any_mouse_up(move |_e, _w, _c| {
-                                                    *counter_up.borrow_mut() += 1;
-                                                })
-                                                .on_mouse_move(move |_e, _w, _c| {
-                                                    *counter_move.borrow_mut() += 1;
-                                                })
-                                                .on_scroll_wheel(|_e, _w, _c| {}),
-                                        ),
-                                ),
-                            ),
-                    ),
-                )
-        }
-    }
-
-    let (_probe, cx) = cx.add_window_view(|_window, cx| TrackFocusProbe {
-        focus: cx.focus_handle(),
-        on_up_counter: counter_for_up,
-        on_move_counter: counter_for_move,
-    });
-    cx.run_until_parked();
-
-    cx.simulate_mouse_move(point(px(400.0), px(400.0)), None, Modifiers::default());
-    cx.run_until_parked();
-    cx.simulate_click(point(px(400.0), px(400.0)), Modifiers::default());
-    cx.run_until_parked();
-
-    assert!(
-        *move_count.borrow() > 0,
-        "Bisect layer 5: input_overlay's on_mouse_move never fired even \
-         though the cursor was simulated over it. The same `is_hovered` \
-         check fails for every listener, exactly mirroring the T7 red \
-         test's observation that hover_point is None."
-    );
-    assert_eq!(
-        *click_count.borrow(),
-        1,
-        "Bisect layer 5: capture_any_mouse_up did not fire under the \
-         full track_focus + bubble-mouse_up root chain. This isolates \
-         the culprit to the root-level listeners that ElyShell adds \
-         around its widget tree."
-    );
-}
-
-/// Bisect probe layer 4: same shape as the canvas-sibling probe but
-/// the on_mouse_down listener calls `cx.update` on a self-entity
-/// (mirroring `down_entity.update(cx, |shell, _| shell.focus_web_surface(window))`).
-/// `entity.update` notifies subscribers; if that side effect during
-/// mouse_down's bubble phase disturbs mouse dispatch — invalidates
-/// the rendered_frame, regenerates hitboxes, or otherwise corrupts
-/// the in-flight dispatch — the subsequent MouseUp will land on a
-/// frame whose hitboxes no longer match the listeners' captured
-/// snapshots, and this test will go red.
-#[gpui::test]
-async fn baseline_overlay_with_entity_update_in_mouse_down_receives_click(cx: &mut TestAppContext) {
-    let click_count = Rc::new(RefCell::new(0u32));
-    let counter_for_render = click_count.clone();
-
-    struct EntityUpdateProbe {
-        on_up_counter: Rc<RefCell<u32>>,
-        tick: u32,
-    }
-    impl Render for EntityUpdateProbe {
-        fn render(&mut self, _window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
-            let counter = self.on_up_counter.clone();
-            let self_entity = cx.entity().clone();
-            div()
-                .relative()
-                .size_full()
-                .min_w_0()
-                .overflow_hidden()
-                .child(div().absolute().inset_0().child(div().size_full()))
-                .child(
-                    canvas(move |_bounds, _window, _cx| {}, |_, _, _, _| {}).absolute().size_full(),
-                )
-                .child(
-                    div()
-                        .absolute()
-                        .size_full()
-                        .occlude()
-                        .on_mouse_down(MouseButton::Left, move |_event, _window, cx| {
-                            self_entity.update(cx, |probe, _cx| {
-                                probe.tick += 1;
-                            });
-                        })
-                        .capture_any_mouse_up(move |_event, _window, _cx| {
-                            *counter.borrow_mut() += 1;
-                        })
-                        .on_mouse_move(|_event, _window, _cx| {})
-                        .on_scroll_wheel(|_event, _window, _cx| {}),
-                )
-        }
-    }
-
-    let (_probe, cx) = cx.add_window_view(|_window, _cx| EntityUpdateProbe {
-        on_up_counter: counter_for_render,
-        tick: 0,
-    });
-    cx.run_until_parked();
-
-    cx.simulate_mouse_move(point(px(400.0), px(400.0)), None, Modifiers::default());
-    cx.simulate_click(point(px(400.0), px(400.0)), Modifiers::default());
-    cx.run_until_parked();
-
-    assert_eq!(
-        *click_count.borrow(),
-        1,
-        "Bisect layer 4: on_mouse_down's bubble fires entity.update \
-         which automatically notifies subscribers. If this test fails, \
-         the cx.notify side effect during in-flight dispatch corrupts \
-         the rendered_frame for the immediately-following MouseUp."
-    );
-}
-
-/// Bisect probe layer 3: add a canvas sibling BEFORE the overlay,
-/// matching render_web_surface's viewport_tracker sibling exactly.
-/// The canvas's prepaint callback fires during paint phase; if it
-/// somehow disturbs hitbox registration or mouse_listeners ordering,
-/// this test will go red and pinpoint the suspect.
-#[gpui::test]
-async fn baseline_overlay_with_canvas_sibling_receives_click(cx: &mut TestAppContext) {
-    let click_count = Rc::new(RefCell::new(0u32));
-    let counter_for_render = click_count.clone();
-
-    struct CanvasSiblingProbe {
-        on_up_counter: Rc<RefCell<u32>>,
-    }
-    impl Render for CanvasSiblingProbe {
-        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
-            let counter = self.on_up_counter.clone();
-            div()
-                .relative()
-                .size_full()
-                .min_w_0()
-                .overflow_hidden()
-                .child(div().absolute().inset_0().child(div().size_full()))
-                .child(
-                    canvas(move |_bounds, _window, _cx| {}, |_, _, _, _| {}).absolute().size_full(),
-                )
-                .child(
-                    div()
-                        .absolute()
-                        .size_full()
-                        .occlude()
-                        .on_mouse_down(MouseButton::Left, |_event, _window, _cx| {})
-                        .capture_any_mouse_up(move |_event, _window, _cx| {
-                            *counter.borrow_mut() += 1;
-                        })
-                        .on_mouse_move(|_event, _window, _cx| {})
-                        .on_scroll_wheel(|_event, _window, _cx| {}),
-                )
-        }
-    }
-
-    let (_probe, cx) =
-        cx.add_window_view(|_window, _cx| CanvasSiblingProbe { on_up_counter: counter_for_render });
-    cx.run_until_parked();
-
-    cx.simulate_mouse_move(point(px(400.0), px(400.0)), None, Modifiers::default());
-    cx.simulate_click(point(px(400.0), px(400.0)), Modifiers::default());
-    cx.run_until_parked();
-
-    assert_eq!(
-        *click_count.borrow(),
-        1,
-        "Bisect layer 3: adding a canvas sibling (the shape \
-         render_viewport_tracker uses) between the content wrapper and \
-         the overlay should not break click delivery. If this fails, \
-         the canvas element itself disturbs mouse dispatch — likely \
-         via its prepaint callback's interaction with hit_test."
-    );
-}
-
-#[gpui::test]
-async fn baseline_overlay_with_full_listener_combo_receives_click(cx: &mut TestAppContext) {
-    let click_count = Rc::new(RefCell::new(0u32));
-    let counter_for_render = click_count.clone();
-
-    struct ComboProbe {
-        on_up_counter: Rc<RefCell<u32>>,
-    }
-    impl Render for ComboProbe {
-        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
-            let counter = self.on_up_counter.clone();
-            div().relative().size_full().child(
-                div()
-                    .absolute()
-                    .size_full()
-                    .occlude()
-                    .on_mouse_down(MouseButton::Left, |_event, _window, _cx| {})
-                    .capture_any_mouse_up(move |_event, _window, _cx| {
-                        *counter.borrow_mut() += 1;
-                    })
-                    .on_mouse_move(|_event, _window, _cx| {})
-                    .on_scroll_wheel(|_event, _window, _cx| {}),
-            )
-        }
-    }
-
-    let (_probe, cx) =
-        cx.add_window_view(|_window, _cx| ComboProbe { on_up_counter: counter_for_render });
-    cx.run_until_parked();
-
-    cx.simulate_mouse_move(point(px(100.0), px(100.0)), None, Modifiers::default());
-    cx.simulate_click(point(px(100.0), px(100.0)), Modifiers::default());
-    cx.run_until_parked();
-
-    assert_eq!(
-        *click_count.borrow(),
-        1,
-        "GPUI baseline with input_overlay's full listener combo: click should \
-         reach capture_any_mouse_up. If this fails, the listener combo itself \
-         is the problem, not the surrounding shell."
-    );
-}
-
-#[gpui::test]
-async fn baseline_overlay_div_receives_simulated_click(cx: &mut TestAppContext) {
-    let click_count = Rc::new(RefCell::new(0u32));
-    let counter_for_render = click_count.clone();
-
-    struct Probe {
-        on_up_counter: Rc<RefCell<u32>>,
-    }
-    impl Render for Probe {
-        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
-            let counter = self.on_up_counter.clone();
-            div().relative().size_full().child(
-                div().absolute().size_full().occlude().capture_any_mouse_up(
-                    move |_event, _window, _cx| {
-                        *counter.borrow_mut() += 1;
-                    },
-                ),
-            )
-        }
-    }
-
-    let (_probe, cx) =
-        cx.add_window_view(|_window, _cx| Probe { on_up_counter: counter_for_render });
-    cx.run_until_parked();
-
-    cx.simulate_mouse_move(point(px(100.0), px(100.0)), None, Modifiers::default());
-    cx.simulate_click(point(px(100.0), px(100.0)), Modifiers::default());
-    cx.run_until_parked();
-
-    assert_eq!(
-        *click_count.borrow(),
-        1,
-        "GPUI baseline: a div with .absolute().size_full().occlude() and \
-         capture_any_mouse_up never received the simulated click. The test \
-         harness or GPUI primitive is broken — ElyShell test results are \
-         meaningless until this passes."
-    );
-}
-
-/// TDD red guard for T10: today every `WebSurfaceFrame::from_live_frame`
-/// call allocates a fresh `Arc::new(RenderImage::new(...))` regardless
-/// of whether the underlying pixels changed. At 60 fps on a 1080p
-/// canvas that is `~8 MB / frame` of host-side RGBA cloning + a new
-/// GPUI texture upload, the cost Linus + Karpathy + Jony all flagged
-/// as the next material bottleneck after the file-system pipe.
-///
-/// The contract this test pins is the cheapest invariant we can hold
-/// against today's `SoftwareRenderingContext`: two frames carrying
-/// **byte-identical RGBA payloads must produce the same underlying
-/// `Arc<RenderImage>`**. Today they do not — every `from_live_frame`
-/// blindly reallocates. The fix path is either dedup the upload
-/// against the last bytes or switch to direct platform-surface presentation.
-///
-/// Regression guard: with the single-slot `LAST_FRAME_IMAGE` cache in
-/// `web_surface_frame.rs`, two `ServoLiveFrame` inputs carrying
-/// byte-identical RGBA payloads now share the same `Arc<RenderImage>`.
-/// Without this guard a regression that drops the cache silently
-/// returns to ~960 MB/s of host-side RGBA cloning + per-frame GPUI
-/// texture allocations.
-#[test]
-fn identical_live_frames_share_render_image_arc() -> Result<(), String> {
-    let width = 16u32;
-    let height = 8u32;
-    let rgba_bytes = vec![0xAAu8; (width as usize) * (height as usize) * 4];
-
-    let first = WebSurfaceFrame::from_live_frame(
-        "https://example.com/".to_string(),
-        WebSurfaceScrollOffset::default(),
-        100,
-        ServoLiveFrame::for_test(width, height, rgba_bytes.clone()),
-    )
-    .map_err(|error| error.to_string())?;
-    let second = WebSurfaceFrame::from_live_frame(
-        "https://example.com/".to_string(),
-        WebSurfaceScrollOffset::default(),
-        100,
-        ServoLiveFrame::for_test(width, height, rgba_bytes),
-    )
-    .map_err(|error| error.to_string())?;
-
-    let first_image = first
-        .image
-        .as_ref()
-        .ok_or_else(|| "software path must produce an Arc<RenderImage>".to_string())?;
-    let second_image = second
-        .image
-        .as_ref()
-        .ok_or_else(|| "software path must produce an Arc<RenderImage>".to_string())?;
-    assert!(
-        Arc::ptr_eq(first_image, second_image),
-        "TDD red: two ServoLiveFrames with byte-identical RGBA produced \
-         distinct Arc<RenderImage> instances (first={:p}, second={:p}). \
-         WebSurfaceFrame::from_parts must dedup the upload against the \
-         previous frame's bytes, or the rendering pipeline must switch \
-         to direct platform-surface presentation so per-frame host \
-         allocations stop entirely.",
-        Arc::as_ptr(first_image),
-        Arc::as_ptr(second_image),
-    );
-    assert!(first.has_same_software_render_as(&second));
-    Ok(())
-}
-
 fn active_tab_overlay_state(
     shell: &gpui::Entity<super::ElyShell>,
     cx: &mut gpui::VisualTestContext,
@@ -1060,3 +468,8 @@ fn active_tab_overlay_state(
 fn example_url() -> Result<UrlText, ely_domain::DomainError> {
     UrlText::parse("https://example.com/".to_string())
 }
+
+#[path = "gpui_harness_tests_b.rs"]
+mod gpui_harness_tests_b;
+#[path = "gpui_harness_tests_c.rs"]
+mod gpui_harness_tests_c;
diff --git a/crates/ely_app/src/shell/gpui_harness_tests_b.rs b/crates/ely_app/src/shell/gpui_harness_tests_b.rs
new file mode 100644
index 0000000..69e8ed8
--- /dev/null
+++ b/crates/ely_app/src/shell/gpui_harness_tests_b.rs
@@ -0,0 +1,319 @@
+use super::*;
+
+/// Bisect probe layer 2: stack the full ElyShell wrapper chain that
+/// sits between the window root and the overlay — root size_full,
+/// absolute inset_0 flex container, flex_1 + flex_col main pane with
+/// rounded/border/shadow/overflow_hidden, flex_1 content wrapper,
+/// then the relative+overflow_hidden surface wrapper from
+/// `render_web_surface`. If this passes, the bug is in something
+/// `render_external_web_canvas` adds (not in the plain layout chain).
+#[gpui::test]
+async fn baseline_overlay_under_full_elyshell_wrapper_chain_receives_click(
+    cx: &mut TestAppContext,
+) {
+    let click_count = Rc::new(RefCell::new(0u32));
+    let counter_for_render = click_count.clone();
+
+    struct DeepProbe {
+        on_up_counter: Rc<RefCell<u32>>,
+    }
+    impl Render for DeepProbe {
+        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+            let counter = self.on_up_counter.clone();
+            // Root: matches render_browser's outer div.
+            div().size_full().child(
+                // Absolute flex container matches render_browser's child layout.
+                div().absolute().inset_0().p(px(16.0)).gap(px(12.0)).flex().child(
+                    // Main pane: matches render_main_pane.
+                    div()
+                        .flex_1()
+                        .h_full()
+                        .min_w_0()
+                        .flex()
+                        .flex_col()
+                        .rounded(px(18.0))
+                        .border_1()
+                        .overflow_hidden()
+                        .child(
+                            // Content wrapper: matches the flex_1 child of main_pane.
+                            div().flex_1().overflow_hidden().child(
+                                // Surface wrapper: matches render_web_surface root.
+                                div().relative().size_full().min_w_0().overflow_hidden().child(
+                                    div()
+                                        .absolute()
+                                        .size_full()
+                                        .occlude()
+                                        .on_mouse_down(MouseButton::Left, |_event, _window, _cx| {})
+                                        .capture_any_mouse_up(move |_event, _window, _cx| {
+                                            *counter.borrow_mut() += 1;
+                                        })
+                                        .on_mouse_move(|_event, _window, _cx| {})
+                                        .on_scroll_wheel(|_event, _window, _cx| {}),
+                                ),
+                            ),
+                        ),
+                ),
+            )
+        }
+    }
+
+    let (_probe, cx) =
+        cx.add_window_view(|_window, _cx| DeepProbe { on_up_counter: counter_for_render });
+    cx.run_until_parked();
+
+    cx.simulate_mouse_move(point(px(400.0), px(400.0)), None, Modifiers::default());
+    cx.simulate_click(point(px(400.0), px(400.0)), Modifiers::default());
+    cx.run_until_parked();
+
+    assert_eq!(
+        *click_count.borrow(),
+        1,
+        "Bisect layer 2: the full root → absolute-flex → main-pane → \
+         content-wrapper → surface-wrapper chain (sans listeners) \
+         should still deliver the click. If this fails, the bug is in \
+         this wrapper chain itself; if it passes, the bug is in \
+         something render_external_web_canvas adds (canvas tracker, \
+         absolute content wrapper sibling, or a gpui-component widget)."
+    );
+}
+
+/// Diagnostic probes (T13 bisect): each layer of the ElyShell render
+/// tree was reproduced in isolation and **all passed**, confirming the
+/// listener combo, layout wrapper chain, canvas sibling, entity
+/// update side effects, and track_focus root listeners are NOT the
+/// cause. The bug is elsewhere — likely in ElyShell::new's setup
+/// (subscriptions, timer, InputState side effects) or in the
+/// sync_address_input call inside navigate_active_tab that mutates
+/// Input widget state which may invalidate the rendered_frame
+/// between MouseMove and MouseUp. Kept for regression coverage.
+/// T13 layer 6: replicate ElyShell::new's gpui-component widget
+/// construction (InputState creation + subscription) on top of the
+/// passing layout, then click. If this fails, the InputState entity
+/// or its subscription is what breaks hit_test for descendant
+/// occlude divs.
+#[gpui::test]
+async fn baseline_overlay_with_input_state_construction_receives_click(cx: &mut TestAppContext) {
+    use gpui::AppContext;
+    use gpui::Entity;
+    use gpui::Subscription;
+    use gpui_component::input::{InputEvent, InputState};
+
+    cx.update(gpui_component::init);
+
+    let click_count = Rc::new(RefCell::new(0u32));
+    let counter_for_render = click_count.clone();
+
+    struct ProbeWithInput {
+        on_up_counter: Rc<RefCell<u32>>,
+        _command_input: Entity<InputState>,
+        _command_subscription: Subscription,
+    }
+    impl Render for ProbeWithInput {
+        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+            let counter = self.on_up_counter.clone();
+            div().relative().size_full().min_w_0().overflow_hidden().child(
+                div()
+                    .absolute()
+                    .size_full()
+                    .occlude()
+                    .on_mouse_down(MouseButton::Left, |_e, _w, _c| {})
+                    .capture_any_mouse_up(move |_e, _w, _c| {
+                        *counter.borrow_mut() += 1;
+                    })
+                    .on_mouse_move(|_e, _w, _c| {})
+                    .on_scroll_wheel(|_e, _w, _c| {}),
+            )
+        }
+    }
+
+    let (_probe, cx) = cx.add_window_view(|window, cx| {
+        let command_input = cx.new(|cx| InputState::new(window, cx).placeholder("test"));
+        let command_subscription = cx.subscribe_in(
+            &command_input,
+            window,
+            |_probe: &mut ProbeWithInput, _input, _event: &InputEvent, _window, _cx| {
+                // mimic the shape ElyShell::new uses
+            },
+        );
+        ProbeWithInput {
+            on_up_counter: counter_for_render,
+            _command_input: command_input,
+            _command_subscription: command_subscription,
+        }
+    });
+    cx.run_until_parked();
+
+    cx.simulate_mouse_move(point(px(400.0), px(400.0)), None, Modifiers::default());
+    cx.simulate_click(point(px(400.0), px(400.0)), Modifiers::default());
+    cx.run_until_parked();
+
+    assert_eq!(
+        *click_count.borrow(),
+        1,
+        "Bisect layer 6: an InputState entity + a subscribe_in to it \
+         must not break click delivery to a sibling occlude div. If \
+         this fails, the InputState construction (which spawns \
+         BlinkCursor, registers window-activation/focus/blur \
+         observers) corrupts hit_test for the rest of the tree."
+    );
+}
+
+/// T13 next-layer diagnostic: same shape as the passing baseline
+/// (`.relative().size_full().min_w_0().overflow_hidden()` parent +
+/// the input_overlay listener combo) but with `gpui_component::init`
+/// called first. The real ElyShell test calls init; the probes
+/// don't. If this fails, `gpui_component::init`'s side effect on
+/// the App is what breaks the rendered_frame's hitbox registration
+/// for descendant occlude divs.
+#[gpui::test]
+async fn baseline_overlay_after_gpui_component_init_receives_click(cx: &mut TestAppContext) {
+    cx.update(gpui_component::init);
+
+    let click_count = Rc::new(RefCell::new(0u32));
+    let counter_for_render = click_count.clone();
+
+    struct AfterInitProbe {
+        on_up_counter: Rc<RefCell<u32>>,
+    }
+    impl Render for AfterInitProbe {
+        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+            let counter = self.on_up_counter.clone();
+            div().relative().size_full().min_w_0().overflow_hidden().child(
+                div()
+                    .absolute()
+                    .size_full()
+                    .occlude()
+                    .on_mouse_down(MouseButton::Left, |_e, _w, _c| {})
+                    .capture_any_mouse_up(move |_e, _w, _c| {
+                        *counter.borrow_mut() += 1;
+                    })
+                    .on_mouse_move(|_e, _w, _c| {})
+                    .on_scroll_wheel(|_e, _w, _c| {}),
+            )
+        }
+    }
+
+    let (_probe, cx) =
+        cx.add_window_view(|_window, _cx| AfterInitProbe { on_up_counter: counter_for_render });
+    cx.run_until_parked();
+
+    cx.simulate_mouse_move(point(px(400.0), px(400.0)), None, Modifiers::default());
+    cx.simulate_click(point(px(400.0), px(400.0)), Modifiers::default());
+    cx.run_until_parked();
+
+    assert_eq!(
+        *click_count.borrow(),
+        1,
+        "Bisect: gpui_component::init must not break click delivery to \
+         an occlude div with the input_overlay listener combo. If this \
+         fails, init registers some App-level state that interferes \
+         with rendered_frame hitbox registration for descendants."
+    );
+}
+
+/// Bisect probe layer 5: the full chain WITH the root-level
+/// `track_focus + on_mouse_up(Left, bubble)` listeners ElyShell
+/// puts on its outermost div. If track_focus's auto-focus MouseDown
+/// handler, or the root's bubble-phase MouseUp listener, somehow
+/// invalidates the rendered_frame between MouseDown and MouseUp,
+/// input_overlay's hitbox will no longer match the listener
+/// snapshot's id and `is_hovered` will return false. That's the
+/// exact symptom we see: hover_point is None too, so it's not
+/// capture-specific — every listener on input_overlay is missing
+/// its hit.
+#[gpui::test]
+async fn baseline_overlay_under_root_with_track_focus_receives_click(cx: &mut TestAppContext) {
+    use gpui::FocusHandle;
+
+    let click_count = Rc::new(RefCell::new(0u32));
+    let move_count = Rc::new(RefCell::new(0u32));
+    let counter_for_up = click_count.clone();
+    let counter_for_move = move_count.clone();
+
+    struct TrackFocusProbe {
+        focus: FocusHandle,
+        on_up_counter: Rc<RefCell<u32>>,
+        on_move_counter: Rc<RefCell<u32>>,
+    }
+    impl Render for TrackFocusProbe {
+        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+            let counter_up = self.on_up_counter.clone();
+            let counter_move = self.on_move_counter.clone();
+            div()
+                .size_full()
+                .track_focus(&self.focus)
+                .on_mouse_up(MouseButton::Left, |_event, _window, _cx| {})
+                .child(
+                    div().absolute().inset_0().p(px(16.0)).gap(px(12.0)).flex().child(
+                        div()
+                            .flex_1()
+                            .h_full()
+                            .min_w_0()
+                            .flex()
+                            .flex_col()
+                            .rounded(px(18.0))
+                            .border_1()
+                            .overflow_hidden()
+                            .child(
+                                div().flex_1().overflow_hidden().child(
+                                    div()
+                                        .relative()
+                                        .size_full()
+                                        .min_w_0()
+                                        .overflow_hidden()
+                                        .child(div().absolute().inset_0().child(div().size_full()))
+                                        .child(
+                                            canvas(move |_b, _w, _c| {}, |_, _, _, _| {})
+                                                .absolute()
+                                                .size_full(),
+                                        )
+                                        .child(
+                                            div()
+                                                .absolute()
+                                                .size_full()
+                                                .occlude()
+                                                .on_mouse_down(MouseButton::Left, |_e, _w, _c| {})
+                                                .capture_any_mouse_up(move |_e, _w, _c| {
+                                                    *counter_up.borrow_mut() += 1;
+                                                })
+                                                .on_mouse_move(move |_e, _w, _c| {
+                                                    *counter_move.borrow_mut() += 1;
+                                                })
+                                                .on_scroll_wheel(|_e, _w, _c| {}),
+                                        ),
+                                ),
+                            ),
+                    ),
+                )
+        }
+    }
+
+    let (_probe, cx) = cx.add_window_view(|_window, cx| TrackFocusProbe {
+        focus: cx.focus_handle(),
+        on_up_counter: counter_for_up,
+        on_move_counter: counter_for_move,
+    });
+    cx.run_until_parked();
+
+    cx.simulate_mouse_move(point(px(400.0), px(400.0)), None, Modifiers::default());
+    cx.run_until_parked();
+    cx.simulate_click(point(px(400.0), px(400.0)), Modifiers::default());
+    cx.run_until_parked();
+
+    assert!(
+        *move_count.borrow() > 0,
+        "Bisect layer 5: input_overlay's on_mouse_move never fired even \
+         though the cursor was simulated over it. The same `is_hovered` \
+         check fails for every listener, exactly mirroring the T7 red \
+         test's observation that hover_point is None."
+    );
+    assert_eq!(
+        *click_count.borrow(),
+        1,
+        "Bisect layer 5: capture_any_mouse_up did not fire under the \
+         full track_focus + bubble-mouse_up root chain. This isolates \
+         the culprit to the root-level listeners that ElyShell adds \
+         around its widget tree."
+    );
+}
+
diff --git a/crates/ely_app/src/shell/gpui_harness_tests_c.rs b/crates/ely_app/src/shell/gpui_harness_tests_c.rs
new file mode 100644
index 0000000..98611c9
--- /dev/null
+++ b/crates/ely_app/src/shell/gpui_harness_tests_c.rs
@@ -0,0 +1,276 @@
+use super::*;
+
+/// Bisect probe layer 4: same shape as the canvas-sibling probe but
+/// the on_mouse_down listener calls `cx.update` on a self-entity
+/// (mirroring `down_entity.update(cx, |shell, _| shell.focus_web_surface(window))`).
+/// `entity.update` notifies subscribers; if that side effect during
+/// mouse_down's bubble phase disturbs mouse dispatch — invalidates
+/// the rendered_frame, regenerates hitboxes, or otherwise corrupts
+/// the in-flight dispatch — the subsequent MouseUp will land on a
+/// frame whose hitboxes no longer match the listeners' captured
+/// snapshots, and this test will go red.
+#[gpui::test]
+async fn baseline_overlay_with_entity_update_in_mouse_down_receives_click(cx: &mut TestAppContext) {
+    let click_count = Rc::new(RefCell::new(0u32));
+    let counter_for_render = click_count.clone();
+
+    struct EntityUpdateProbe {
+        on_up_counter: Rc<RefCell<u32>>,
+        tick: u32,
+    }
+    impl Render for EntityUpdateProbe {
+        fn render(&mut self, _window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
+            let counter = self.on_up_counter.clone();
+            let self_entity = cx.entity().clone();
+            div()
+                .relative()
+                .size_full()
+                .min_w_0()
+                .overflow_hidden()
+                .child(div().absolute().inset_0().child(div().size_full()))
+                .child(
+                    canvas(move |_bounds, _window, _cx| {}, |_, _, _, _| {}).absolute().size_full(),
+                )
+                .child(
+                    div()
+                        .absolute()
+                        .size_full()
+                        .occlude()
+                        .on_mouse_down(MouseButton::Left, move |_event, _window, cx| {
+                            self_entity.update(cx, |probe, _cx| {
+                                probe.tick += 1;
+                            });
+                        })
+                        .capture_any_mouse_up(move |_event, _window, _cx| {
+                            *counter.borrow_mut() += 1;
+                        })
+                        .on_mouse_move(|_event, _window, _cx| {})
+                        .on_scroll_wheel(|_event, _window, _cx| {}),
+                )
+        }
+    }
+
+    let (_probe, cx) = cx.add_window_view(|_window, _cx| EntityUpdateProbe {
+        on_up_counter: counter_for_render,
+        tick: 0,
+    });
+    cx.run_until_parked();
+
+    cx.simulate_mouse_move(point(px(400.0), px(400.0)), None, Modifiers::default());
+    cx.simulate_click(point(px(400.0), px(400.0)), Modifiers::default());
+    cx.run_until_parked();
+
+    assert_eq!(
+        *click_count.borrow(),
+        1,
+        "Bisect layer 4: on_mouse_down's bubble fires entity.update \
+         which automatically notifies subscribers. If this test fails, \
+         the cx.notify side effect during in-flight dispatch corrupts \
+         the rendered_frame for the immediately-following MouseUp."
+    );
+}
+
+/// Bisect probe layer 3: add a canvas sibling BEFORE the overlay,
+/// matching render_web_surface's viewport_tracker sibling exactly.
+/// The canvas's prepaint callback fires during paint phase; if it
+/// somehow disturbs hitbox registration or mouse_listeners ordering,
+/// this test will go red and pinpoint the suspect.
+#[gpui::test]
+async fn baseline_overlay_with_canvas_sibling_receives_click(cx: &mut TestAppContext) {
+    let click_count = Rc::new(RefCell::new(0u32));
+    let counter_for_render = click_count.clone();
+
+    struct CanvasSiblingProbe {
+        on_up_counter: Rc<RefCell<u32>>,
+    }
+    impl Render for CanvasSiblingProbe {
+        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+            let counter = self.on_up_counter.clone();
+            div()
+                .relative()
+                .size_full()
+                .min_w_0()
+                .overflow_hidden()
+                .child(div().absolute().inset_0().child(div().size_full()))
+                .child(
+                    canvas(move |_bounds, _window, _cx| {}, |_, _, _, _| {}).absolute().size_full(),
+                )
+                .child(
+                    div()
+                        .absolute()
+                        .size_full()
+                        .occlude()
+                        .on_mouse_down(MouseButton::Left, |_event, _window, _cx| {})
+                        .capture_any_mouse_up(move |_event, _window, _cx| {
+                            *counter.borrow_mut() += 1;
+                        })
+                        .on_mouse_move(|_event, _window, _cx| {})
+                        .on_scroll_wheel(|_event, _window, _cx| {}),
+                )
+        }
+    }
+
+    let (_probe, cx) =
+        cx.add_window_view(|_window, _cx| CanvasSiblingProbe { on_up_counter: counter_for_render });
+    cx.run_until_parked();
+
+    cx.simulate_mouse_move(point(px(400.0), px(400.0)), None, Modifiers::default());
+    cx.simulate_click(point(px(400.0), px(400.0)), Modifiers::default());
+    cx.run_until_parked();
+
+    assert_eq!(
+        *click_count.borrow(),
+        1,
+        "Bisect layer 3: adding a canvas sibling (the shape \
+         render_viewport_tracker uses) between the content wrapper and \
+         the overlay should not break click delivery. If this fails, \
+         the canvas element itself disturbs mouse dispatch — likely \
+         via its prepaint callback's interaction with hit_test."
+    );
+}
+
+#[gpui::test]
+async fn baseline_overlay_with_full_listener_combo_receives_click(cx: &mut TestAppContext) {
+    let click_count = Rc::new(RefCell::new(0u32));
+    let counter_for_render = click_count.clone();
+
+    struct ComboProbe {
+        on_up_counter: Rc<RefCell<u32>>,
+    }
+    impl Render for ComboProbe {
+        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+            let counter = self.on_up_counter.clone();
+            div().relative().size_full().child(
+                div()
+                    .absolute()
+                    .size_full()
+                    .occlude()
+                    .on_mouse_down(MouseButton::Left, |_event, _window, _cx| {})
+                    .capture_any_mouse_up(move |_event, _window, _cx| {
+                        *counter.borrow_mut() += 1;
+                    })
+                    .on_mouse_move(|_event, _window, _cx| {})
+                    .on_scroll_wheel(|_event, _window, _cx| {}),
+            )
+        }
+    }
+
+    let (_probe, cx) =
+        cx.add_window_view(|_window, _cx| ComboProbe { on_up_counter: counter_for_render });
+    cx.run_until_parked();
+
+    cx.simulate_mouse_move(point(px(100.0), px(100.0)), None, Modifiers::default());
+    cx.simulate_click(point(px(100.0), px(100.0)), Modifiers::default());
+    cx.run_until_parked();
+
+    assert_eq!(
+        *click_count.borrow(),
+        1,
+        "GPUI baseline with input_overlay's full listener combo: click should \
+         reach capture_any_mouse_up. If this fails, the listener combo itself \
+         is the problem, not the surrounding shell."
+    );
+}
+
+#[gpui::test]
+async fn baseline_overlay_div_receives_simulated_click(cx: &mut TestAppContext) {
+    let click_count = Rc::new(RefCell::new(0u32));
+    let counter_for_render = click_count.clone();
+
+    struct Probe {
+        on_up_counter: Rc<RefCell<u32>>,
+    }
+    impl Render for Probe {
+        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+            let counter = self.on_up_counter.clone();
+            div().relative().size_full().child(
+                div().absolute().size_full().occlude().capture_any_mouse_up(
+                    move |_event, _window, _cx| {
+                        *counter.borrow_mut() += 1;
+                    },
+                ),
+            )
+        }
+    }
+
+    let (_probe, cx) =
+        cx.add_window_view(|_window, _cx| Probe { on_up_counter: counter_for_render });
+    cx.run_until_parked();
+
+    cx.simulate_mouse_move(point(px(100.0), px(100.0)), None, Modifiers::default());
+    cx.simulate_click(point(px(100.0), px(100.0)), Modifiers::default());
+    cx.run_until_parked();
+
+    assert_eq!(
+        *click_count.borrow(),
+        1,
+        "GPUI baseline: a div with .absolute().size_full().occlude() and \
+         capture_any_mouse_up never received the simulated click. The test \
+         harness or GPUI primitive is broken — ElyShell test results are \
+         meaningless until this passes."
+    );
+}
+
+/// TDD red guard for T10: today every `WebSurfaceFrame::from_live_frame`
+/// call allocates a fresh `Arc::new(RenderImage::new(...))` regardless
+/// of whether the underlying pixels changed. At 60 fps on a 1080p
+/// canvas that is `~8 MB / frame` of host-side RGBA cloning + a new
+/// GPUI texture upload, the cost Linus + Karpathy + Jony all flagged
+/// as the next material bottleneck after the file-system pipe.
+///
+/// The contract this test pins is the cheapest invariant we can hold
+/// against today's `SoftwareRenderingContext`: two frames carrying
+/// **byte-identical RGBA payloads must produce the same underlying
+/// `Arc<RenderImage>`**. Today they do not — every `from_live_frame`
+/// blindly reallocates. The fix path is either dedup the upload
+/// against the last bytes or switch to direct platform-surface presentation.
+///
+/// Regression guard: with the single-slot `LAST_FRAME_IMAGE` cache in
+/// `web_surface_frame.rs`, two `ServoLiveFrame` inputs carrying
+/// byte-identical RGBA payloads now share the same `Arc<RenderImage>`.
+/// Without this guard a regression that drops the cache silently
+/// returns to ~960 MB/s of host-side RGBA cloning + per-frame GPUI
+/// texture allocations.
+#[test]
+fn identical_live_frames_share_render_image_arc() -> Result<(), String> {
+    let width = 16u32;
+    let height = 8u32;
+    let rgba_bytes = vec![0xAAu8; (width as usize) * (height as usize) * 4];
+
+    let first = WebSurfaceFrame::from_live_frame(
+        "https://example.com/".to_string(),
+        WebSurfaceScrollOffset::default(),
+        100,
+        ServoLiveFrame::for_test(width, height, rgba_bytes.clone()),
+    )
+    .map_err(|error| error.to_string())?;
+    let second = WebSurfaceFrame::from_live_frame(
+        "https://example.com/".to_string(),
+        WebSurfaceScrollOffset::default(),
+        100,
+        ServoLiveFrame::for_test(width, height, rgba_bytes),
+    )
+    .map_err(|error| error.to_string())?;
+
+    let first_image = first
+        .image
+        .as_ref()
+        .ok_or_else(|| "software path must produce an Arc<RenderImage>".to_string())?;
+    let second_image = second
+        .image
+        .as_ref()
+        .ok_or_else(|| "software path must produce an Arc<RenderImage>".to_string())?;
+    assert!(
+        Arc::ptr_eq(first_image, second_image),
+        "TDD red: two ServoLiveFrames with byte-identical RGBA produced \
+         distinct Arc<RenderImage> instances (first={:p}, second={:p}). \
+         WebSurfaceFrame::from_parts must dedup the upload against the \
+         previous frame's bytes, or the rendering pipeline must switch \
+         to direct platform-surface presentation so per-frame host \
+         allocations stop entirely.",
+        Arc::as_ptr(first_image),
+        Arc::as_ptr(second_image),
+    );
+    assert!(first.has_same_software_render_as(&second));
+    Ok(())
+}